One cheer for the President's space plan

> RE: " > They are going to increase NASA's budget 5%, but mandate
> space craft
>> that may not be possible to build,
> Why is CEV not possible to build? It's just a stretch Apollo capsule,
> launched on an existing booster (like CRV/OSP), with a mission-specific
> service module. "
>
> I hate to be tedious, but Apollo space craft could go to space and
> back once, so a new one was needed each time. Ditto the boosters.

Actually, the Apollo heat shield was overbuilt (they weren't certain
how thick it needed to be, so they were cautious), so each capsule
could easily have been flown multiple times. The only major change
needed to make the capsule reusable a hundred times or so is either a
replaceable ablative heat shield or a shield made from shuttle type
tiles or RCC. The boosters can be ditched each time. That's the way
it works for satellite launches. Ideally there will be some innovation
aimed at dropping booster costs, but there's no need to make them
reusable. In the longer term it would be nice to have reusable
boosters, but there's no reason to put that on the critical path. The
less innovation in the critical path, the better.

> The Shuttle Orbiters were to be able to make the trip to low Earth
> orbit (only) perhaps 100 times, needing only new external fuel tanks.

...and a near complete rebuild after each flight. The amount of effort
expended getting a shuttle ready for reflight is greater than that
needed to build a new booster and mate it to a capsule. Capsules can
be made reusable much more easily, since they don't see the high total
heat loads of a lifting reentry.

> Having a space craft that would be efficient for going to the ISS and
> also the Moon would be like having an ocean liner that would work
> equally well for crossing a river, like the Mississippi, and also the
> Atlantic ocean. The details are tedious, and it looks easy on Star
> Trek, but no one who known about rockets or boats, would claim that it
> made sense to propose such a vehicle in the abstract. And clearly a
> "stretch Apollo" can not. It would not even be stable on the first
> reentry.

I think you are assuming the CEV would be an all in one - from
O'Keefe's discussion of it it's clear that the CEV would be a basic
life support vehicle with mission specific service modules, so it's
adaptable to different missions. You use a LEO maneuvering module for
ISS servicing, and a high delta-V module for Lunar missions. Almost
certainly there will either be a separate vehicle for lunar landings or
yet another service module for landings. The common element is the
life support section, which presumably includes provisions for reentry.
There is no need for one vehicle to perform all possible missions, but
there is a need for a vehicle family with commonalities that make it
flexible and adaptable.

As far as "stretch Apollo" being unstable on reentry - look at the OSP
brochure here
http://www.slinews.com/images/OSP_ill_HiRes_no_bkgnd.jpg> (warning:
huge picture). The vehicle in the lower left corner is the kind of
thing I'm talking about. It's almost certainly the kind of thing that
CEV will turn out to be. The propulsion module in the image is
suitable for LEO maneuvering. There's no reason it couldn't be swapped
out for a module capable of injection onto a lunar trajectory and
providing support services while working in lunar orbit (which will be
the first step). Now that we know how to do on orbit assembly there's
no reason not to assemble the lunar lander in lunar orbit. By avoiding
a big one size fits all vehicle we gain flexibility.

......Andrew